class_docstr: Passes the encoder state through to the decoder as-is. This bridge
  can only be used if encoder and decoder have the exact same state size, i.e.
  use the same RNN cell.
code: def default_params():
      return {}
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import abc
  from pydoc import locate
  import six
  import numpy
  import tensorflow
  from tensorflow.python.util import nest
  from seq2seq.configurable import Configurable
label_desc: Use image node_id 1 for calling the PassThroughBridge obj's underlying member method code with example usage: obj.default_params() and returns: dict